The present invention relates to two-cycle internal combustion engines, and more particularly to such an engine including a double-acting piston, a precombustion chamber and a translating and rotating crankshaft.
In accordance with the laws of thermodynamics, it is desirable to provide an engine which maximizes pressure and temperature during combustion, as such results in the most efficient conversion of energy. In addition, in accordance with the laws of physics, the power to weight ratio of an engine increases as the speed of engine operation increases.
Unfortunately, a variety of secondary effects make difficult the achievement of an engine which achieves these objectives. As engine speed increases, so do the inertial forces and the stresses placed upon moving parts in the engine. At high speeds, the failure rate of these parts increases. Increasing the size of these parts to increase their strength has limited benefits, as such further increases the inertial forces and the total weight of the engine.
In some instances, current engine designs also do not permit ready solutions to these problems. For a number of reasons, traditional piston rods are much longer than the distance of the entire piston stroke. One advantage arising from a longer piston rods is such permits a longer piston stroke, and thus a higher compression ratio. The longer piston rod also provides greater clearance between the piston and crankshaft at bottom dead center. On the other hand, the longer piston rod is subject to high inertial forces.
A problem with raising engine temperatures and pressures is that the life of parts subjected to these high heat and pressures in the engine are reduced. In order to reduced the detrimental effects of the high heat, today""s engines employ cooling systems. The cooling systems, however, serve to reduce the efficiency of the system.
Another problem with an engine operating at high speed is that the time for combustion is very short. To accommodate combustion time, combustion may be initiated before the piston is at top dead center. Combustion forces generated as the piston moves upwardly to top dead center act against the direction of the piston, contributing to a lower energy level of the engine. On the other hand, if combustion is not initiated until the piston is at top dead center, then total optimum combustion time is very short. As a result, the generated combustion force is limited, and so is the power output of the engine in relation to provided fuel.
Another disadvantage of a short combustion time is that certain less combustible alternative fuels are not usable in these engines. Simply, the combustion time is so short that slower combusting fuels do not sufficiently combust to generate efficient engine power. A problem with existing engines is that the optimal combustion time is so short, that it is detrimental to raise the speed of the engine because optimal combustion time is further shortened. This problem thus prevents achievement of an engine with otherwise higher efficiency by operation at higher speeds.
Two-cycle internal combustion engines have an advantage over four-cycle internal combustion engines in that an entire piston cycle is not lost without producing force. On the other hand, combustion effects are reduced due to incomplete scavenging: not all of the exhaust gasses are exhausted before combustion initiates, and insufficient incoming air is provided for complete combustion of the fuel.
One detrimental side effect of this incomplete combustion of fuel is the exhausting of unburned fuel and undesirable gasses. Due to the emission problems associated with two-cycle engines, in some instances U.S. laws prevent the operation of two-cycle engines.
An engine which is capable of exploiting the advantages of high pressures of combustion, high temperatures of combustion, and high engine speed is desired.
An improved internal combustion engine is disclosed. In one embodiment, the engine is a two-cycle engine with improved performance characteristics.
In one embodiment, the engine is an internal combustion engine including an engine block. Preferably, at least two cylinder heads are mounted to the block. A piston is movably mounted in a cylinder bore defined by each cylinder head. The cylinder bore is generally closed at its top and bottom, whereby the piston divides the bore into a first variable volume intake chamber and a second variable volume combustion chamber. The cylinder head farther defines a precombustion chamber, the precombustion chamber selectively in communication with the first variable volume intake chamber and the second variable volume combustion chamber.
At least one intake port is provided for permitting air to be drawn into the variable volume intake chamber. Air within the variable volume intake chamber is compressed when the piston in the cylinder bore moves downwardly.
At least one passage is provided for selectively permitting the compressed charge of air to flow into the precombustion chamber. Once in the precombustion chamber, the compressed air charge is heated, raising it to yet a higher pressure. A fuel delivery element is adapted to deliver fuel into the compressed air. A passage is provided permitting the fuel and air charge to flow from the precombustion chamber to the variable volume combustion chamber.
At least one valve is provided for selectively opening and closing the passage(s) between the variable volume intake chamber and the precombustion chamber, and the precombustion chamber and variable volume combustion chamber.
Ignition of the fuel and air mixture in the variable volume combustion chamber causes the piston to move downwardly in the cylinder bore. The piston is connected to a crankshaft which is mounted to the engine block.
In one embodiment, the block includes a first block gear and a second block gear. The crankshaft has a first end and a second end and at least one, and preferably two, piston mounting portions located between its ends. Each piston mounting portion is positioned along a first axis offset from a second axis through the first and second ends of the crankshaft. A first crankshaft gear is located at the first end of the crankshaft, the first crankshaft gear engaging the first block gear. A second crankshaft gear is located at the second end of the crankshaft, the second crankshaft gear engaging the second block gear. Movement of the piston causes the crankshaft to rotate about the second axis and the second axis to move in a generally circular pathway.
In one embodiment, the ends of the piston are supported by eccentric bearings. The bearings permit rotation and translation (i.e. movement of the rotational axis of the crankshaft) of the crankshaft.
In one embodiment of the invention, the block has four sides positioned between its ends. A cylinder head is coupled to each of the sides, and a piston is movably mounted in the cylinder bore defined by each head. The crankshaft includes a first piston mounting portion and a second piston mounting portion. A first pair of pistons mounted at opposing sides of the block are connected to one another about the first piston mounting portion. A second pair of pistons mounted at opposing sides of the block are connected to one another about the second piston mounting portion.
In one embodiment, the intake port includes an intake valve adapted to selectively open and close the intake port. A single valve is located in the precombustion chamber. The valve includes a first seal and a second seal. The first seal is adapted to selectively open and close the port or passage between the variable volume intake chamber and the precombustion chamber. The second seal is adapted to selectively open and close the port or passage between the precombustion chamber and the variable volume combustion chamber.
In one embodiment, the valve located in the precombustion chamber is driven by a rocker arm. The rocker arm is, in turn driven by an end of a follower. An opposing end of the follower is driven by a cam which is rotated by the crankshaft.
Another aspect of the invention is a lubricating and cooling system for a piston of an internal combustion engine, the piston having a head and a rod. A first end of the rod is coupled to the head and a second end of the rod is located opposite the first end thereof. A passage extends through the rod from the first end to the second end. An inlet leads from an exterior of the second end to the passage. At least one delivery passage is located in the head and extends from the passage in the head and returns to the passage in the rod. An outlet extends from the passage in rod.
At least one partition divides the passage through the rod into an inlet passage leading from the inlet to the delivery passage and an outlet passage leading from the delivery passage to the outlet. At least one lubrication directing element is located in the inlet passage and outlet passage, the at least one lubrication directing element generally inhibiting the flow of lubricant from the delivery passage to the inlet and from the outlet to the delivery passage.
Upward and downward movement of the piston during engine operation generates a pumping effect. Lubricant is drawn into the inlet and delivered to the head. The lubricant may be delivered through weeps to rings mounted on the exterior of the piston head. Excess lubricant is delivered back to the outlet.
Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached figures.